Many processes for the preparation of halogenoalkanes are known. These are essentially catalyzed and non-catalyzed processes in the gas phase or liquid phase. U.S. Pat. No. 3,981,938, for example, describes the preparation of halogenoalkanes in the liquid phase by reaction of an alkanol with at least a 10% excess of hydrogen halide, the water of reaction obtained being removed at the bottom of the liquid phase reactor as a mixture with alkanol and hydrogen halide. A similar process is known from U.S. Pat. No. 3,983,180, in which methanol is reacted with hydrogen chloride in the liquid phase to give methyl chloride, the concentration of the hydrogen chloride being above the azeotrope concentration. Both processes have the disadvantage that working up of the aqueous solution of hydrogen halide removed from the circulation is cost-intensive and associated with a high expenditure on apparatus.
U.S. Pat. No. 4,366,324 describes a process for the simultaneous preparation of organosiloxanes and methyl chloride from an organochlorosilane and methanol in the liquid phase, the concentration of the hydrogen chloride in the liquid phase being below the azeotrope concentration. The disadvantages of this process lie chiefly in the comparatively low space-time yield and in the relatively high content of the by-product dimethyl ether, which additionally makes purification of the methyl chloride more difficult.
U.S. Pat. No. 4,108,882 discloses a process for the simultaneous preparation of siloxanes and methyl chloride in the gas phase, in which an organochlorosilane and methanol are reacted in the presence of a quaternary ammonium compound as the catalyst, the temperatures and pressure being chosen so that the water formed can escape from the reaction zone, in order to avoid deactivation of the catalyst.
The object of the present invention is to provide a process which enables halogenoalkanes to be prepared in a relatively simple manner and with a high space-time yield, in which the formation of by-products are reduced to a minimum.